90 TWENTIETH CENTURY CLASSICS 



mechanical laws of flight in all their subtle complications, 

 with an ease and gracefulness that seems spiritual. Who 

 can fail to note that fine adjustment of the organs of flight 

 to aerial elasticity and gravitation, by which that aston- 

 ishing bit of nervous energy can rise and fall almost on 

 the perpendicular, dart from side to side, as if by magic, 

 or, assuming the horizontal position, pass out of sight like 

 a shooting star? Is it not impossible to conceive of all 

 this being done by that rational calculation which enables 

 the rower to row, or the sailor to sail his boat ? " 



Their deep, cup-shaped nests are usually built on small, 

 horizontal limbs of trees, six to twelve feet from the 

 ground ; a delicate, beautiful structure, composed of a 

 cottony substance, and soft, silky fibers from plants, the 

 outside dotted over with lichen. Eggs two (varying in 

 size), .48x.33; pure white; in form, rather elliptical. 



XXIV. CHIMNEY SWIFT. 



Chaetura pelagica (LiNN.). 



Summer resident; abundant in the eastern part of the 

 State. Arrive the last of April; begin laying the latter 

 part of May; return in September; a few occasionally 

 remain into October. 



HABITAT. Eastern North America ; north to Labra- 

 dor, Manitoba, etc. ; west to the edge of the plains ; south 

 of the United States in winter to Cozumel Island, Jalapa, 

 Mexico, and possibly farther. 



Iris dark brown ; bill and claws black ; legs and feet 

 brownish black. The above. are fresh measurements of a 

 pair of adult birds, shot in the month of June. From other 



